Systems and methods for calibrating power regulated communication circuitry

ABSTRACT

Systems and methods are provided for calibrating the control mechanism in a communication circuit to allow the communication circuit to maintain a desired output power level. The communication circuit includes a variable gain adjustment circuit and a power amplifier, which operate together to provide an output power level. A control circuit controls the variable gain adjustment circuit based on a default gain parameter, a high power threshold, and a low power threshold. A calibration circuit in the control circuit calibrates a default gain parameter to provide a desired output power. A power detector can detect the desired output power level to provide an output power measurement. The calibration circuit calibrates upper and lower power thresholds to provide an acceptable range of power variation around the output power measurement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Application No. 60/695,342, filed Jun. 30, 2005, U.S.Provisional Application No. 60/708,901, filed Aug. 17, 2005, U.S.Provisional Application No. 60/775,965, filed Feb. 22, 2006, and U.S.Provisional Application No. 60/798,270, filed May 4, 2006, which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

This invention generally relates to wireless communication circuitry andmore particularly to systems and methods for calibrating the outputpower control system in a wireless communication circuit.

Wireless communication devices generally operate based on powerrequirements defined by government regulations or industry standards.Such standards and regulations may require a wireless communicationdevice to produce signals having a prescribed power level. Additionally,communication device manufactures may also have reasons to producesignals having particular power levels.

Several factors may affect the output power level of a wirelesscommunication device. These factors include variations in thecommunication device's component parts, changes in antenna impedance,and changes in environmental conditions, for example. Such factors maycause the output power of the output power level to wander from aprescribed/target power level. Therefore, many communication devicesinclude control mechanisms to ensure that a prescribed/target powerlevel is maintained in a communication device.

Typically, the control mechanism of a communication device needs to becalibrated before it can be used in operation. The control mechanism mayinclude various operating parameters, and the calibration process mayinvolve initialing these parameters to their correct starting values,which in some cases can be an iterative process. The calibration processcan be even more time consuming when a communication device operates atmultiple power levels. For such communication devices calibration mayneed to be performed for each power level.

Even though calibration can be time consuming, it is an importantquality control measure to ensure that a communication device willoperate at the correct power levels. Accordingly, there is continuinginterest in improving calibration processes and in reducing calibrationtimes.

SUMMARY OF THE INVENTION

The disclosed technology provides systems and methods for calibratingthe control mechanism of a communication circuit to allow thecommunication circuit to maintain a desired output power level. Thecommunication circuit includes a variable gain adjustment circuit and apower amplifier, which operate together to provide an output powerlevel. A feedback loop from the output power level to the variable gainadjustment circuit includes a power detector and a control circuit. Thecontrol circuit controls the variable gain adjustment circuit based on adefault gain parameter, a high power threshold, and a low powerthreshold. A calibration circuit in the control circuit calibrates thedefault gain parameter to provide a desired output power when thefeedback loop is disabled. The power detector can detect the desiredoutput power level to provide an output power measurement. With thefeedback loop enabled, the calibration circuit calibrates the upper andlower power thresholds to provide an acceptable range of power variationaround the output power measurement.

In one aspect of the invention; a default gain adjustment circuit canconfigure the default gain parameter to provide a desired output powerlevel while the feedback loop is disabled. The default gain adjustmentcircuit can calibrate the default gain parameter based on knowing aninput-output relationship for the power detector. Additionally, thedefault gain parameter can have a linear relationship with the outputpower. Accordingly, the default gain adjustment circuit can adjust thedefault gain parameter based on the linear relationship until itdetermines that the output power matches a desired output power level.

The power detector can measure the desired output power level to providean output power measurement. A threshold adjustment circuit in thecalibration circuit can calibrate the upper power threshold and thelower power threshold by setting them to initial values and enabling thefeedback loop. The control circuit can adjust a gain tuning parameterbased on comparing the output power measurement with the upper and lowerthresholds. The threshold adjustment circuit can use the gain tuningparameter to adjust the upper and lower thresholds during calibration. Atuning access circuit can be in communication with the gain tuningparameter. In one embodiment, the threshold adjustment circuit can use atable of adjustment values to adjust the upper and lower thresholdsaccording to a predetermined progression. For an iteration, the table ofadjustment values can contain the values

$\left\lbrack {\frac{1}{3}\left( {P_{upper} - P_{lower}} \right)} \right\rbrack,\left\lbrack {\frac{2}{3}\left( {P_{upper} - P_{lower}} \right)} \right\rbrack,\left( {P_{upper} - P_{lower}} \right),{{and}\mspace{14mu}\left\lbrack {\frac{4}{3}\left( {P_{upper} - P_{lower}} \right)} \right\rbrack},$

wherein (P_(upper)−P_(lower)) is the difference between the thresholdvalues in a previous iteration. In one embodiment, the thresholdadjustment can be iterative.

In one aspect of the invention, the threshold adjustment circuit caniteratively adjust the upper and lower power thresholds. In eachiteration, the threshold adjustment circuit can maintain a thresholdvalue range that includes the upper and lower power thresholds. Thethreshold value range can be sub-divided into three sub-ranges thatinclude top, middle, and bottom sub-ranges. The boundaries between thesub-ranges corresponds to the upper and lower power thresholds. Thetuning access circuit can access the gain tuning parameter. If the gaintuning parameter is less than an initial tuning value, the thresholdadjustment circuit can select the top sub-range as the threshold valuerange for the next iteration. If the gain tuning parameter is equal tothe initial tuning value, the threshold adjustment circuit can selectthe middle sub-range as the threshold value range for the nextiteration. If the gain tuning parameter is greater than an initialtuning value, the threshold adjustment circuit can select the bottomsub-range as the threshold value range for the next iteration. Thecalibration circuit can adjust the upper and lower power thresholds tobe within the selected sub-range.

In one aspect of the invention, a calibration means in a control meanscalibrates the default gain parameter to provide a desired output powerwhen the feedback loop is disabled. A power detector means can detectthe desired output power level to provide an output power measurement.With the feedback loop enabled, the calibration means calibrates theupper and lower power thresholds to provide an acceptable range of powervariation around the output power measurement.

A default gain calibration means can configure the default gainparameter to provide a desired output power level while the feedbackloop is disabled. A calibration means can calibrate the default gainparameter based on knowing an input-output relationship for the powerdetector means. Additionally, the default gain parameter can have alinear relationship with the output power. Accordingly, the calibrationmeans can adjust the default gain parameter based on the linearrelationship until it determines that the output power matches a desiredoutput power level.

The power detector means can measure the desired output power level toprovide an output power measurement. The calibration means can calibratethe upper power threshold and the lower power threshold by setting themto initial values, and enabling the feedback loop. The control means canadjust a gain tuning parameter based on comparing the output powermeasurement with the upper and lower thresholds. The calibration meanscan use the gain tuning parameter to adjust the upper and lowerthresholds during calibration. In one embodiment, the calibration meanscan use a table of adjustment values to adjust the upper and lowerthresholds according to a predetermined progression. For an iteration,the table of adjustment values can contain the values

$\left\lbrack {\frac{1}{3}\left( {P_{upper} - P_{lower}} \right)} \right\rbrack,\left\lbrack {\frac{2}{3}\left( {P_{upper} - P_{lower}} \right)} \right\rbrack,\left( {P_{upper} - P_{lower}} \right),$

and

$\left\lbrack {\frac{4}{3}\left( {P_{upper} - P_{lower}} \right)} \right\rbrack,$

wherein (P_(upper)−P_(lower)) is the difference between the thresholdvalues in a previous iteration. In one embodiment, the thresholdadjustment can be iterative.

In one aspect of the invention, the calibration means can iterativelyadjust the upper and lower power thresholds. In each iteration, thecalibration means can maintain a threshold value range that includes theupper and lower power thresholds. The threshold value range can besub-divided into three sub-ranges that include top, middle, and bottomsub-ranges. The boundaries between the sub-ranges corresponds to theupper and lower power thresholds. If the gain tuning parameter is lessthan an initial tuning value, the calibration means can select the topsub-range as the threshold value range for the next iteration. If thegain tuning parameter is equal to the initial tuning value, thecalibration means can select the middle sub-range as the threshold valuerange for the next iteration. If the gain tuning parameter is greaterthan an initial tuning value, the calibration means can select thebottom sub-range as the threshold value range for the next iteration.The calibration means can adjust the upper and lower power thresholds tobe within the selected sub-range.

In one aspect of the invention, a calibration program running on aprocessor can calibrate the default gain parameter to provide a desiredoutput power when the feedback loop is disabled. A power detector candetect the desired output power level to provide an output powermeasurement. With the feedback loop enabled, a calibration programrunning on a processor can calibrate the upper and lower powerthresholds to provide an acceptable range of power variation around theoutput power measurement.

A default gain calibration program running on a processor can configurethe default gain parameter to provide a desired output power level whilethe feedback loop is disabled. A calibration program can calibrate thedefault gain parameter based on knowing an input-output relationship forthe power detector. Additionally, the default gain parameter can have alinear relationship with the output power. Accordingly, the calibrationprogram can adjust the default gain parameter based on the linearrelationship until it determines that the output power matches a desiredoutput power level.

The power detector can measure the desired output power level to providean output power measurement. The calibration program running on aprocessor can calibrate the upper power threshold and the lower powerthreshold by setting them to initial values and enabling the feedbackloop. A control program running on a processor can adjust a gain tuningparameter based on comparing the output power measurement with the upperand lower thresholds. The calibration program can use the gain tuningparameter to adjust the upper and lower thresholds during calibration.In one embodiment, the calibration program can use a table of adjustmentvalues to adjust the upper and lower thresholds according to apredetermined progression. For an iteration, the table of adjustmentvalues can contain the values

$\left\lbrack {\frac{1}{3}\left( {P_{upper} - P_{lower}} \right)} \right\rbrack,\left\lbrack {\frac{2}{3}\left( {P_{upper} - P_{lower}} \right)} \right\rbrack,\left( {P_{upper} - P_{lower}} \right),{{and}\mspace{14mu}\left\lbrack {\frac{4}{3}\left( {P_{upper} - P_{lower}} \right)} \right\rbrack},$

wherein (P_(upper)−P_(lower)) is the difference between the thresholdvalues in a previous iteration. In one embodiment, the thresholdadjustment can be iterative.

In one aspect of the invention, the calibration program can iterativelyadjust the upper and lower power thresholds. In each iteration, thecalibration program can maintain a threshold value range that includesthe upper and lower power thresholds. The threshold value range can besub-divided into three sub-ranges that include top, middle, and bottomsub-ranges. The boundaries between the sub-ranges corresponds to theupper and lower power thresholds. If the gain tuning parameter is lessthan an initial tuning value, the calibration program can select the topsub-range as the threshold value range for the next iteration. If thegain tuning parameter is equal to the initial tuning value, thecalibration program can select the middle sub-range as the thresholdvalue range for the next iteration. If the gain tuning parameter isgreater than an initial tuning value, the calibration program can selectthe bottom sub-range as the threshold value range for the nextiteration. The calibration program can adjust the upper and lower powerthresholds to be within the selected sub-range.

Further features of the invention, its nature and various advantages,will be more apparent from the accompanying drawings and the followingdetailed description of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary communication circuit inaccordance with one aspect of the invention;

FIG. 2 is a graph of an exemplary input-output relationship of the powerdetector of FIG. 1;

FIG. 3 is a graph of an exemplary region defined by upper and lowerpower thresholds;

FIG. 4 is a flow diagram of one embodiment of calibrating the controlcircuitry of FIG. 1;

FIG. 5 is a flow diagram of one embodiment of calibrating a default gainparameter;

FIG. 6 is a diagram of exemplary upper and lower threshold values beforeand after calibration;

FIG. 7A is a flow diagram of one embodiment of calibrating upper andlower power threshold values;

FIG. 7B is a flow diagram of one embodiment of adjusting thresholdvalues;

FIG. 8 is a graph of an exemplary progression that can be used tocalibrate upper and lower power threshold values in accordance with FIG.7B;

FIG. 9 is a flow diagram of one embodiment of adjusting upper and lowerthreshold values during calibration;

FIG. 10 is a flow diagram of one embodiment of adjusting upper and lowerthreshold values during calibration that is a continuation of FIG. 9;

FIG. 11 is an exemplary progression of adjusted upper and lower powerthreshold values;

FIG. 12A is a block diagram of an exemplary high definition televisionthat can employ the disclosed technology;

FIG. 12B is a block diagram of an exemplary vehicle that can employ thedisclosed technology;

FIG. 12C is a block diagram of an exemplary cell phone that can employthe disclosed technology;

FIG. 12D is a block diagram of an exemplary set top box that can employthe disclosed technology; and

FIG. 12E is a block diagram of an exemplary media player that can employthe disclosed technology.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a block diagram of one embodiment ofa communication circuit 100 in accordance with one aspect of theinvention. The communication circuit 100 includes a variable gainadjustment (VGA) circuit 102 and a power amplifier 104. As used herein,a variable gain adjustment circuit 102 refers to a circuit that operatesto receive an input signal and that is operable to adjust an amplitudeof the input signal. The adjustment may increase the amplitude, which isreferred to as gain, or may decrease the amplitude, which is referred toas attenuation. Attenuation produces the opposite effect of gain andtherefore can essentially be characterized as “negative gain.”Accordingly, the term “variable gain adjustment” as used herein refersgenerally to signal adjustment that can correspond to positive gain ornegative gain (i.e., attenuation). As used herein, the term “poweramplifier” refers to a circuit that receives an input signal and that isoperable to increase the power of the input signal. A variable gainadjustment circuit 102 and a power amplifier 104 can be implementedusing existing technology that will be known to one skilled in the art.

A VGA circuit 102 can be used to regulate the output power to remainwithin a desirable range of output power levels. In one embodiment, apower amplifier 104 can also be adjusted as required to regulate outputpower. One way to control the output power may be by varying the gain ofthe VGA circuit 102. In one embodiment of a VGA circuit 102, eachdiscrete step adjustment in the gain may correspond to a discrete changein output power level at the output of the power amplifier 104. In oneexample, a single step increase in the gain of the VGA circuit 102 mayresult in a 0.5 dB increase in output power level.

The communication circuit 100 includes a feedback loop from the outputof the power amplifier 104 to the variable gain adjustment circuitry102. The feedback loop operates to control the VGA circuit 102 in a waythat regulates the output power level. The feedback loop includes apower detector circuit 106 connected to the output of the poweramplifier that can provide a measurement of the output power. A controlcircuit 108 in the feedback loop receives the output power measurementand makes a determination regarding whether the measurement isacceptable. If the measurement is not acceptable, the control circuit108 can adjust the VGA circuit 102 to provide an appropriate amount ofsignal adjustment that will result in an acceptable output power level.From hereon, the power level at the output of the power amplifier 104will be referred to herein as “true output power” and the measurementprovided by the power detector will be referred to as an “output powermeasurement.” The determination of whether or not a output powermeasurement corresponding to a true output power is acceptable will bedescribed in more detail in connection with FIG. 3.

An output power measurement can depend on various factors, such as thetime and duration over which true output power is measured and themethods used by the power detector for making such a measurement. In oneexample of measurement timing, a signal at the output of the poweramplifier 104 may represent digital information in the format ofpackets. In one embodiment, some degree of consistency betweenmeasurements can be provided by measuring the true output power over theduration of a packet communication. In one embodiment, several instancesof the true output power can be measured and averaged to provide anaveraged output power measurement. In various embodiments, the outputpower measurement may be a DC, pseudo-DC or a low frequency signal. Oneembodiment of a power detector is described in U.S. patent applicationSer. No. 10/673,263, filed Sep. 30, 2003, which is hereby incorporatedherein by reference in its entirety.

FIG. 2 shows one embodiment of an input-output relationship for a powerdetector circuit 106. As previously described herein, the power detector106 can measure the true output power to provide an output powermeasurement. FIG. 2 shows an exponential relationship 202 between theoutput power measurement and the output voltage.

A non-linear relationship 202 between true output power and the outputpower measurements may complicate the control mechanism. For example, inthe illustrated relationship 202 of FIG. 2, variation in the true outputpower for higher true output power values 204 will result in largervariations in the output power measurements, whereas the same variationsin the true output power for lower true output power values 206 willresult in smaller variations in the output power measurements. A controlcircuit may or may not take this non-linearity into consideration. FIG.2 is exemplary and other input-output relationship for a power detectorare contemplated. For example, in some embodiments, the relationshipbetween the measured output power and the true output power can belinear or can correspond to another relationship such as a higher-orderpolynomial.

Referring again to FIG. 1, the control circuit 108 can receive an outputpower measurement from the power detector 106 and make a determinationregarding whether the output power measurement is acceptable. In theillustrated embodiment and in accordance with one aspect of theinvention, the determination of acceptability of the output powermeasurement can be based on an upper power threshold 110 and a lowerpower threshold 112. Also with reference to FIG. 3, an output powermeasurement provided by a power detector 106 can have a maximum valuePD_(max) and a minimum value PD_(min). The upper power thresholdP_(upper) 110 and the lower power threshold P_(lower) 112 can define aparticular range of values in the output power measurement range inwhich the output power measurement is acceptable. If the output powermeasurement varies within this range, the control circuit 108 canmaintain the VGA circuit 102 at its existing configuration. However, ifthe output power measurement wanders outside of this range, the controlcircuit 108 can adjust the VGA circuit 102 to force the output powermeasurement back into the acceptable range. For example, if the outputpower measurement is greater than P_(upper) 110, the control circuit 108can reduce the gain in the VGA circuit 102 to lower the true outputpower, and if the output power measurement is less than P_(lower) 112,the control circuit 108 can increase the gain in the VGA circuit 102 toincrease the true output power.

The use of an upper power threshold 110 and a lower power threshold 112allows the control circuit 106 to avoid unnecessarily adjusting the VGAcircuit 102. As previously described herein, true output power can bemeasured over the duration of a packet. The measurements can vary fromone packet to another because of variations in the content of thepacket. By providing an upper power threshold 110 and a lower powerthreshold 112, the control circuit 108 can allow for measurementvariations that flow from the natural operation of the communicationcircuit 100, which are not variations that need to be corrected. Abenefit of using two thresholds over using only a single threshold isthat the control circuitry 108 will not need to constantly adjust theVGA circuitry 102 if the output power measurement oscillates minutelyaround a desired output power level.

Referring again to FIG. 1 and in accordance with one aspect of theinvention, the control circuit 108 can control the VGA circuitry 102based on a default gain parameter 114 and a gain tuning parameter 116.The control circuitry 108 can use the default gain parameter 114 toprovide a baseline level of gain at the VGA circuit 102. When thecontrol circuitry 108 is first calibrated, the default gain parameter114 can be configured to provide a desired true output power level,which can correspond to a output power measurement within the acceptablerange (e.g., as shown in FIG. 3). After calibration, the default gainparameter 114 can remain unchanged, but the output power measurementscan wander outside the acceptable range (e.g., as shown in FIG. 3)because of various factors (e.g., environmental conditions) in oraffecting the communication device 100.

The control circuit 108 can use the gain tuning parameter 116 to adjustthe VGA circuit 102 when the output power measurements becomeunacceptable. In one embodiment, the control circuit 108 can control theVGA circuit 102 based on a sum of the default gain parameter 114 and thegain tuning parameter 116. The gain tuning parameter 114 can be set toan initial value during calibration. After calibration, the controlcircuit 108 can increase the gain tuning parameter 116 to increase thegain of the VGA circuit 102 or decrease the gain tuning parameter 116 todecrease the gain of the VGA circuit 102. In one embodiment, thecommunication device 100 can be configured so that discrete changes inthe gain tuning parameter 116 correspond to discrete changes in the trueoutput power. For example, the communication device 100 can beconfigured so that each increase of one step in the gain tuningparameter 116 results in approximately 0.5 dBm change in the true outputpower, and each decrease of one step in the gain tuning parameter 116results in approximately a −0.5 dBm change in the true output power. Inother embodiments, the change in true output power in relation to achange in the gain tuning parameter 116 may have a different proportionor may not be linear.

What has been described thus far are systems and methods for controllinga communication circuit to provide a desired output power level. Thecontrol circuit 108 provides the control operation based on an upperpower threshold 110, a lower power threshold 112, a default gainparameter 114, and a gain tuning parameter 116, which can be stored inmemory registers in the control circuit 108. In certain embodiments, thedefault gain parameter 114 and/or the gain tuning parameter 116 can bestored in the variable gain adjustment (VGA) circuit 102, and thecontrol circuit 108 can access the VGA circuit 102 to access theirvalues. The values of the default gain parameter 114, the upper powerthreshold 110, and the lower power threshold 112 can be determinedduring a calibration process for a particular desired output powerlevel. In one embodiment, a communication circuit 100 may operate atdifferent power levels if multiple communication channels are available.As used herein, a “channel” refers to communication using a particularfrequency. A communication device 100 can be capable of operating atdifferent frequencies so that one communication device 100 can be usedfor communications over multiple channels. Different channels may havedifferent output power level requirements. In one embodiment,calibration is performed for one output power level for one channel at atime. In other embodiments, calibration can be performed simultaneouslyfor more than one channel.

FIGS. 4-11 will now describe the calibration process for determining thevalues of the default gain parameter, the upper power threshold, and thelower power threshold for one output power level for a single channel.At least a portion of the following aspects of the invention can beperformed by a calibration circuit 118. In one embodiment, asillustrated in FIG. 1, the calibration circuit 118 can be located in thecontrol circuitry 108. In other embodiments (not shown), the calibrationcircuitry need not be in the control circuitry 108 and can be located inanother portion of the communication circuit 100. In yet anotherembodiment (not shown), the calibration circuitry 108 may not be locatedin the communication circuit 100 and may be connected or coupled to thecommunication circuit 100 when calibration needs to be performed.

Referring now to FIG. 4, there is shown one aspect of the invention forcalibrating the default gain parameter, the upper power threshold, andthe lower power threshold. In the illustrated embodiment, thecalibration begins by calibrating the default gain parameter for adesired true output power level 402. During this portion 402 of thecalibration, the feedback loop can be disabled by, for example,maintaining the gain tuning parameter at an initial tuning value (e.g.,zero). Therefore, the gain tuning parameter does not react to anychanges in the output power measurement, and any changes in the trueoutput power is based only on the default gain parameter. Calibration ofthe default gain parameter is described in more detail in connectionwith FIG. 5. After the default gain parameter is calibrated, thecommunication circuit will be configured to provide a desired trueoutput power level. Using the calibrated default gain parameter, thecontrol circuit can enable the feedback loop 404 and calibrate the highpower threshold value and the low power threshold value 406. Thiscalibration is described in more detail in connection with FIGS. 6-11.The calibration process can finish after these three parameters arecalibrated.

Referring now to FIG. 5, one embodiment of calibrating a default gainparameter is shown. Calibration of the default gain parameter may beneeded because a particular value of the default gain parameter may notalways correspond to a particular true output power. This can be causedby variations in the manufacturing process or by variations fromcomponent to component. For example, a first communication deviceaccording to FIG. 1 may be able to produce twenty dBm of true outputpower using a default gain parameter of five. However, a secondcommunication device according to FIG. 1 may produce only nineteen dBmusing a default gain parameter of five. Although such variations exist,the value of the default gain parameter for a particular true outputpower level will generally be similar between devices. Accordingly, aninitial value can generally be estimated for the default gain parameter.

The calibration process can disable the feedback loop by, for example,maintaining the gain tuning parameter at substantially an initial tuningvalue when calibrating the default gain parameter 502, and the defaultgain parameter can be set to an initial value 504. The true output powerat the output of the power amplifier can be measured 506, and if thetrue output power is substantially equal to a desired output power level508, the calibration is complete. However, if the true output power isnot the same as the desired output power 508, the calibration circuitcan adjust the default gain parameter to produce the desired outputpower 510. As described above herein, the communication circuit can beconfigured so that each discrete change in the default gain parametercorresponds to a discrete change in the true output power. Thecalibration circuit may know this relationship. Therefore, thecalibration circuit can change the default gain parameter by the properamount to adjust the true output power 510. In one embodiment, thediscrete change in the true output power may be limited by the step sizeof the VGA circuit. For example, the desired output may be twenty dBm,and a default gain parameter value of five may provide nineteen dBm oftrue output power. The calibration circuit may know that each change of0.1 in the default gain parameter produces a 0.5 dBm change in the trueoutput power. Therefore, the calibration circuit can increase thedefault gain parameter to 5.2 to provide a true output power of twentydBm. In one embodiment, the calibration circuit can take additionalmeasurements of the true output power 506 to ensure that the adjustmentwas correct 508 and can make further adjustments 510 if necessary. Inone embodiment, the calibration circuit may make only one adjustment tothe default gain parameter 510.

In one embodiment, if the calibration circuit knows the relationshipbetween the true output power and the output power measurements (e.g.,FIG. 2), the calibration circuit can determine the value of the trueoutput power based on the output power measurements. In one embodiment,the input-output relationship of the power detection (e.g., FIG. 2) canbe stored as a table in a memory in the calibration circuit, and thepower detector (FIG. 1, 106) can be calibrated to operate in accordancewith this relationship. In one embodiment, if the calibration circuitdoes not know the relationship (e.g., FIG. 2), the calibration circuitcan be configured to know the input-output relationship of astandardized laboratory power meter. Such a standardized laboratorypower meter can be used to measure the true output power, and an outputpower measurement can be communicated to the calibration circuit. In oneembodiment, the input-output relationship of the standardized laboratorypower meter can be stored as a table in a memory in the calibrationcircuit. Based on the known input-output relationship for thestandardized power meter, the calibration circuit can determine the trueoutput power using the output power measurement. The calibration circuitcan then, adjust the default gain parameter accordingly 510.

FIGS. 6-11 illustrate various aspects of calibrating an upper powerthreshold and a lower power threshold value in accordance with aspectsof the invention. FIG. 6 shows the output power measurement rangepreviously shown in FIG. 3. After calibrating the default gainparameter, the default gain parameter operates to provide a desiredoutput-power measurement, as shown in FIG. 6. The process of calibratingthe upper power threshold and the lower power threshold determines theplacement of the threshold values around the desired output powermeasurement that would allow the control, circuit to regulate the trueoutput power. In the illustrated embodiment of FIG. 6, the upper powerthreshold and the lower power threshold can be set to initial values.During calibration, the threshold values can be changed to become thecalibrated threshold values shown in FIG. 6.

FIG. 7A shows one embodiment of calibrating the upper and lowerthreshold values. As described above herein, the upper and lowerthreshold values can be set to initial values 702, and the gain tuningparameter is equal to an initial tuning value. From hereon, it will beassumed that the initial tuning value is zero 704. The feedback loop canbe enabled so that the control circuit can use the thresholds todetermine if the output power measurement is acceptable (i.e., betweenthe threshold values) 706. If the output power measurement is notacceptable, the natural operation of the feedback loop can cause thecontrol circuit to adjust the gain tuning parameter 708 to adjust theoutput power measurement towards the acceptable range.

It is important to recognize here that, before calibrating the upper andlower power thresholds, the calibrated default gain parameter togetherwith a gain tuning parameter value of zero produced the desired outputpower measurement. Therefore, in one embodiment, one calibrationcompletion condition can require the gain tuning parameter to be zero.This condition will be described in more detail in connection with FIG.11.

The gain tuning parameter can also serve another role. In oneembodiment, the calibration circuit can adjust the upper power thresholdand the lower power threshold based on the gain tuning parameter 710. Ifthe gain tuning parameter is greater than zero, that is an indicationthat the desired output power measurement was less than the lower powerthreshold. Accordingly, the calibration circuit can decrease the lowerpower threshold. At the same time, the calibration circuit can alsodecrease the upper power threshold 710. On the other hand, if the gaintuning parameter is less than zero, that is an indication that thedesired output power measurement was greater than the upper powerthreshold. Accordingly, the calibration circuit can increase the upperpower threshold. At the same time, the calibration circuit can alsoincrease the lower power threshold 710. In one embodiment, the amount ofeach adjustment 710 can be made based on a predetermined progression,which will be described in more detail in connection with FIG. 7B andFIG. 8. The predetermine progression can be implemented by hardwarecircuitry, by computer instructions executing on a processor, or by acombination thereof. In one embodiment, one or more aspects of thepredetermined progression can be stored in a memory (not shown), whichcan be accessed by the hardware circuitry and/or a processor. The memorymay be in the communication circuit (100, FIG. 1) or may be separatefrom the communication circuit.

After the upper and lower threshold values are adjusted 710, thecalibration circuit can determine if one or more completion conditionsare met 712. As described above herein, one completion condition canrequire the gain tuning parameter to be zero. In one embodiment, anothercompletion condition can require the upper and lower threshold values tohave a particular difference or to have at least or at most a particulardifference. If the completion conditions are not met, the thresholdcalibration process can be repeated by resetting the gain tuningparameter to zero 704 and allowing the feedback loop to operate usingthe updated threshold values 706-708. In one embodiment, a completioncondition can be met following a certain number of repetitions of thethreshold calibration process.

FIG. 7B illustrates one embodiment of adjusting threshold values. Theoutput power measurement range (e.g., output power measurement range ofFIG. 6) can be set as the full range of allowable output power values714. The full range of allowable output power values can depend on manyfactors; including hardware limitations and communication channelrestrictions. The initial upper and lower threshold values are selectedfrom this output power measurement range. Final upper and lowerthreshold values also fall within this output power measurement range.The output power measurement range extends from a minimum output powerto a maximum output power and is divided into sub-ranges 716. Eachsub-range comprises a plurality of output power values and can beclassified as an upper, middle or lower range. In one embodiment (e.g.,shown in FIG. 8), each sub-range is a third of the output powermeasurement range. During threshold calibration, initial values forupper and lower, thresholds are selected from the output powermeasurement range. In one embodiment, the initial upper threshold valueis the output power value on the boundary between the upper and middlesub-range. In such an embodiment, the lower threshold value is theoutput power value on the boundary between the lower and middlesub-range. In each iteration of the threshold calibration process ofFIG. 7A, the threshold values are updated depending on at least themeasured output power and the gain tuning parameter. As noted earlier, acompletion condition can be met if a certain number of iterations of thethreshold calibration process have been completed 718. If the completionconditions are met, the threshold calibration process is stopped 720. Ifthe completion conditions are not met and the certain number ofiterations has, not been completed, the upper and low threshold valuesare adjusted based, at least in part, on the value of the gain tuningparameter.

If the gain tuning parameter is greater than zero, then at least one ofthe threshold values is considered too high. Accordingly, the thresholdvalues are adjusted for the next iteration. In particular, if the gaintuning parameter is greater than zero, the threshold values for the nextiteration are selected from the lower sub-range 722. If the gain tuningparameter is less than zero, then at least one of the threshold valuesis considered too low. Accordingly, the threshold values for the nextiteration are selected from the upper sub-range 722. If the gain tuningparameter is equal to zero, the threshold values are selected from themiddle sub-range 722. Based on the gain tuning parameter, the selectedsub-range serves as a new output power range 724 for the next iteration.In the next iteration, the new range (e.g., upper, lower, or middlesub-range) is further divided into smaller sub-ranges 716 and thecalibration process is repeated until a completion condition is reached.

Referring now to FIG. 8, there is shown one embodiment of apredetermined progression for adjusting threshold values in accordancewith the flow diagram of FIG. 7B. The graph of FIG. 8 shows divisions ofthe output power measurement range into equal portions of thirds 806. Inthe illustrated embodiment, the initial value for the upper powerthreshold 802 can be approximately

$\left\lbrack {{PD}_{\min} + {\frac{2}{3}\left( {{PD}_{\max} - {PD}_{\min}} \right)}} \right\rbrack,$

or one third of the way from PD_(max) to PD_(min), and the initial valuefor the lower power threshold 804 can be approximately

$\left\lbrack {{PD}_{\min} + {\frac{1}{3}\left( {{PD}_{\max} - {PD}_{\min}} \right)}} \right\rbrack,$

or one-third of the way from PD_(min) to PD_(max). Accordingly, theinitial threshold values 802, 804 apportion the output power measurementrange into thirds 806. In the next iteration (iteration one), each third806 from the previous iteration is further apportioned into thirds 808,creating nine regions. The upper and lower threshold values in iterationone can correspond to the boundaries of one of the nine portions 808. Inthe next iteration (iteration two), each third 808 from the previousiteration is further apportioned to thirds 810, creating twenty-sevenregions. The upper and lower threshold values in iteration two cancorrespond to the boundaries of one of the twenty-seven portions 810. Inone embodiment, the progression of decreasing the difference between theupper and lower thresholds can progress for only a particular number ofiterations, after which the upper and lower thresholds can maintain thesame difference even if their values are adjusted. For example, in theillustration, the graph can maintain a maximum of twenty-seven regions810 after iteration two. In one embodiment, a predetermined progressionof threshold adjustments can be stored in a memory in the calibrationcircuit. In one embodiment, the predetermined progression can beimplemented in hardware or by machine instructions operating on aprocessor. FIG. 8 is exemplary and variations and other progressions arecontemplated. For example, each iteration need not have three equalregions. For example, based on a non-linear relationship between trueoutput power and output power relationship, as shown in FIG. 2, theregions for lower output power measurements can be smaller and theregions for higher output power measurements can be larger, so that eachregion can approximately correspond to the same difference in trueoutput power.

FIGS. 9-10 illustrate one embodiment of adjusting upper and lower powerthresholds according to the graph of FIG. 8. When the calibration blockreaches the threshold adjustment procedure (710, FIG. 7A), the upper andlower power thresholds can correspond to the boundaries of a particularregion 902. If the difference between the upper and lower thresholdshave not reached a minimum difference 904, then the adjustment canfurther decrease the difference between the thresholds 908-812. If thedifference between the upper and lower thresholds have reached a minimumdifference 904, then the adjustment can change the thresholds withoutdecreasing the difference between the thresholds (916, 918, FIG. 10).

If the difference between the upper and lower thresholds have notreached a minimum difference 904, the calibration block can determine ifthe gain tuning parameter is greater than, equal to, or less than zero906. If the gain tuning parameter is less than zero 908, then the upperand lower thresholds are increased by ⅔Δ and 4/3Δ, respectively, whereΔ=P_(upper)−P_(lower). If the gain tuning parameter is equal to zero910, then the upper power threshold is decreased by ⅓Δ and the lowerpower threshold is increased by ⅓Δ. If the gain tuning parameter isgreater than zero 912, then the upper and lower thresholds are decreasedby 4/3Δ and ⅔Δ, respectively.

Referring now to FIG. 10, if the difference between the upper and lowerthresholds have reached a minimum difference, the calibration block candetermine if the gain tuning parameter is greater than, equal to, orless than zero 914. If the gain tuning parameter is less than zero 916,then the upper and lower thresholds are both increased by Δ. If the gaintuning parameter is greater than zero 918, then both the upper and lowerthresholds are decreased by Δ. If the gain tuning parameter is equal tozero, then no change needs to be made and the calibration should becomplete.

FIG. 11 shows an example of progressing through the calibrationiterations in accordance with FIGS. 7A, 9 and 10. The dotted-linerepresents the desired output power measurement based on a calibrateddefault gain parameter and a gain tuning parameter value of zero.Initially, the upper and lower thresholds are set to the initialthresholds. The gain tuning parameter decreases by one step because thedesired output power measurement is greater than the upper powerthreshold. The negative gain tuning parameter causes both the upper andlower thresholds to increase in accordance with FIG. 9, resulting in thethreshold values shown in iteration one. In iteration one, the gaintuning parameter is reset to zero (704, FIG. 7A). Afterwards, the gaintuning parameter increases by one step because the desired output powermeasurement is less than the lower power threshold. The positive gaintuning parameter causes both the upper and lower thresholds to decreasein accordance with FIG. 9, resulting in the threshold values shown initeration two. In iteration two, the gain tuning parameter is reset tozero (704, FIG. 7A). Afterwards, the gain tuning parameter decreases byone step because the desired output power measurement is greater thanthe upper power threshold. In the illustrated embodiment, the differencebetween the thresholds do not decrease after iteration two. Therefore,the negative gain tuning parameter in this iteration causes both theupper and lower thresholds to be adjusted in accordance with FIG. 10, asshown in iteration three, but their difference is maintained. Thenegative gain tuning parameter causes both the upper and lowerthresholds to be increased in accordance with FIG. 10, as shown initeration three. In iteration three, the gain tuning parameter is resetto zero (710, FIG. 7A). Afterwards, the gain tuning parameter stays atzero because the desired output power measurement is within theacceptable range. Accordingly, the high and lower thresholds are notadjusted and the calibration can end.

Accordingly, what has been described thus far are systems and methodsfor calibrating the control mechanism in a communication circuit toallow the communication circuit to maintain a desired true output power.A calibration circuit in the communication circuit calibrates a defaultgain parameter to provide a desired true output power that correspondsto a desired output power measurement. Then, the calibration circuitcalibrates upper and lower power thresholds to provide an acceptablerange of power variation around the desired output power measurement.

In accordance with one aspect of the invention, once calibration hasbeen performed for a desired output power level, calibration need not beperformed for other desired output levels for the same communicationcircuit. Rather, the parameters for other desired output power levelscan be estimated using interpolation techniques and can be stored in thecontrol circuit.

In one embodiment, the default gain parameter for other desired trueoutput power levels can be computed based on a calibrated default gainparameter. For example, suppose a calibrated default gain parameter of5.2 provides a true output power of twenty dBm, and the communicationcircuit is configured so that each 0.1 change in the default gainparameter corresponds to a 0.5 dBm change in the true output power. Thedefault gain parameter can be computed for another true output power bydirect computation. For example, if a second desired true output poweris thirty dBm, then it can be computed that an increase in the defaultgain parameter of two will increase the true output power by ten dBm,resulting in a true output power of thirty dBm.

In one embodiment, upper and lower threshold values for another trueoutput power level can also be computed. A linear interpolationtechnique can result in a poor estimate if the input-output relationshipof the power detector circuit is non-linear (e.g., FIG. 2). Inaccordance with one aspect of the invention, upper and lower powerthresholds for other desired power levels can be computed using anon-linear, relationship suitable for approximating the input-outputrelationship of the power detector circuit. Exemplary relationshipsinclude third order polynomials or higher-order polynomials.

Referring now to FIGS. 12A-12E, various exemplary implementations of thepresent invention are shown.

Referring now to FIG. 12A, the present invention can be implemented in ahigh definition television (HDTV) 1020. The present invention mayimplement either or both signal processing and/or control circuits,which are generally identified in FIG. 12A at 1022, a WLAN interfaceand/or mass data storage of the HDTV 1020. The HDTV 1020 receives HDTVinput signals in either, a wired or wireless format and generates HDTVoutput signals for a display 1026. In some implementations, signalprocessing circuit and/or control circuit 1022 and/or other circuits(not shown) of the HDTV 1020 may process data, perform coding and/orencryption, perform calculations, format data and/or perform any othertype of HDTV processing that may be required.

The HDTV 1020 may communicate with mass data storage 1027 that storesdata in a nonvolatile manner such as optical and/or magnetic storagedevices. The HDD may be a mini HDD that includes one or more plattershaving a diameter that is smaller than approximately 1.8″. The HDTV 1020may be connected to memory 1028 such as RAM, ROM, low latencynonvolatile memory such as flash memory and/or other suitable electronicdata storage. The HDTV 1020 also may support connections with a WLAN viaa WLAN network interface 1029.

Referring now to FIG. 12B, the present invention implements a controlsystem of a vehicle 1030, a WLAN interface and/or mass data storage ofthe vehicle control system. In some implementations, the presentinvention may implement a powertrain control system 1032 that receivesinputs from one or more sensors such as temperature sensors; pressuresensors, rotational sensors, airflow sensors and/or any other suitablesensors and/or that generates one or more output control signals such asengine operating parameters, transmission operating parameters, and/orother control signals.

The present invention may also be implemented in other control systems1040 of the vehicle 1030. The control system 1040 may likewise, receivesignals from input sensors 1042 and/or output control signals to one ormore output devices 1044. In some implementations, the control system1040 may be part of an anti-lock braking system (ABS), a navigationsystem, a telematics system, a vehicle telematics system, a lanedeparture system, an adaptive cruise control system, a vehicleentertainment system such as a stereo, DVD, compact disc and the like.Still other implementations are contemplated.

The powertrain control system 1032 may communicate with mass datastorage 1046 that stores data in a nonvolatile manner. The mass datastorage 1046 may include optical and/or magnetic storage devices forexample hard disk drives HDD and/or DVDs. The HDD may be a mini HDD thatincludes one or more platters having a diameter that is smaller thanapproximately 1.8″. The powertrain control system 1032 may be connectedto memory 1047 such as RAM, ROM, low latency nonvolatile memory such asflash memory and/or other suitable electronic data storage. Thepowertrain control system 1032 also may support connections with a WLANvia a WLAN network interface 1048. The control system 1040 may alsoinclude mass data storage, memory and/or a WLAN interface (all notshown).

Referring now to FIG. 12C, the present invention can be implemented in acellular phone 1050 that may include a cellular antenna 1051. Thepresent invention may implement either or both signal processing and/orcontrol circuits, which are generally identified in FIG. 12C at 1052, aWLAN interface and/or mass data storage of the cellular phone 1050. Insome implementations, the cellular phone 1050 includes a microphone1056, an audio output 1058 such as a speaker and/or audio output jack, adisplay 1060 and/or an input device 1062 such as a keypad, pointingdevice, voice actuation and/or other input device. The signal processingand/or control circuits 1052 and/or other circuits (not shown) in thecellular phone 1050 may process data, perform coding and/or encryption,perform calculations, format data and/or perform other cellular phonefunctions.

The cellular phone 1050 may communicate with mass data storage 1064 thatstores data in a nonvolatile manner such as optical and/or magneticstorage devices for example hard disk drives HDD and/or DVDs. The HDDmay be a mini HDD that includes one or more platters having a diameterthat is smaller than approximately 1.8″. The cellular phone 1050 may beconnected to memory 1066 such as RAM, ROM, low latency nonvolatilememory such as flash memory and/or other suitable electronic datastorage. The cellular phone 1050 also may support connections with aWLAN via a WLAN network interface 1068.

Referring now to FIG. 12D, the present invention can be implemented in aset top box 1080. The present invention may implement either or bothsignal processing and/or control circuits, which are generallyidentified in FIG. 12D at 1084, a WLAN interface and/or mass datastorage of the set top box 1080. The set top box 1080 receives signalsfrom a source such as a′ broadband source and outputs standard and/orhigh definition audio/video signals suitable for a display 1088 such asa television and/or monitor and/or other video and/or audio outputdevices. The signal processing and/or control circuits 1084 and/or othercircuits (not shown) of the set top box 1080 may process data, performcoding and/or encryption, perform calculations, format data and/orperform any other set top box function.

The set top box 1080 may communicate with mass data storage 1090 thatstores data in a nonvolatile manner. The mass data storage 1090 mayinclude optical and/or magnetic storage devices for example hard diskdrives HDD and/or DVDs. The HDD may be a mini HDD that includes one ormore platters having a diameter that is smaller than approximately 1.8″.The set top box 1080 may be connected to memory 1094 such as RAM, ROM,low latency nonvolatile memory such as flash-memory and/or othersuitable electronic data storage. The set top box 1080 also may supportconnections with a WLAN via a WLAN network interface 1096.

Referring now to FIG. 12E, the present invention can be implemented in amedia player 1100. The present invention may implement either or bothsignal processing and/or control circuits, which are generallyidentified in FIG. 12E at 1104, a WLAN interface and/or mass datastorage of the media player 1100. In some implementations, the mediaplayer 1100 includes a display 1107 and/or a user input 1108 such as akeypad, touchpad and the like. In some implementations, the media player1100 may employ a graphical user interface (GUI) that typically employsmenus, drop down menus, icons and/or a point-and-click interface via thedisplay 1107 and/or user input 1108. The media player 1100 furtherincludes an audio output 1109 such as a speaker and/or audio outputjack. The signal processing and/or control circuits 1104 and/or othercircuits (not shown) of the media player 1100 may process data, performcoding and/or encryption, perform calculations, format data and/orperform any other media player function.

The media player 1100 may communicate with mass data storage 1110 thatstores data such as compressed audio and/or video content in anonvolatile manner. In some implementations, the compressed audio filesinclude files that are compliant with MP3 format or other suitablecompressed audio and/or video formats. The mass data storage may includeoptical and/or magnetic storage devices for example hard disk drives HDDand/or DVDs. The HDD may be a mini HDD that includes one or moreplatters having a diameter that is smaller than approximately 1.8″. Themedia player 1100 may be connected to memory 1114 such as RAM, ROM, lowlatency nonvolatile memory such as flash memory and/or other suitableelectronic data storage. The media player 1100 also may supportconnections with a WLAN via a WLAN network interface 1116. Still otherimplementations in addition to those described above are contemplated.

Accordingly, what have been described thus far are methods and systemsfor calibrating the control circuit of a communication circuit. Thedisclosed methods, components, and circuits can be implemented usingvarious analog and digital circuit means, including circuitry made fromvarious types, sizes, and/or configurations of transistors, MOStransistors, field effect transistors, BJTs, diodes, resistors,capacitors, inductors, integrated circuits, operation amplifiers,operational transconductance amplifiers, comparators, and/or currentsources. The disclosed methods and circuits can also be implementedusing a computing architecture having a processor and machineinstructions executing on the processor. The disclosed embodiments andillustrations are exemplary and do not limit the scope of the disclosedinvention as defined by the following claims.

1-28. (canceled)
 29. A method for calibrating output power ofcommunication circuitry that includes a gain tuning parameter and afeedback loop at the communication circuitry, wherein the gain tuningparameter adjusts the output power of the communication circuitry, themethod comprising: setting the gain tuning parameter to an initialtuning value; enabling the feedback loop at the communication circuitry;and while the feedback loop is enabled, performing a plurality ofiterations at the communication circuitry for adjusting the gain tuningparameter of the communication circuitry based on the output power ofthe communication circuitry.
 30. The method of claim 29, wherein thecommunication circuitry further comprises a default gain parameter, themethod further comprising: disabling the feedback loop; while thefeedback loop is disabled: setting the default gain parameter to a firstvalue; measuring the output power of the communication circuitry toprovide a measurement of the output power; comparing the output powermeasurement to a desired output power level; and setting the defaultgain parameter to a second value based on the comparison.
 31. The methodof claim 30, wherein the default gain parameter and the output powerhave a linear relationship, and wherein setting the default gainparameter to a second value based on the comparison comprises: applyingthe relationship to a difference between the output power measurementand the desired output power to provide a gain parameter difference; andapplying the gain parameter difference to the default gain parameter toset the default gain parameter to the second value.
 32. The method ofclaim 29, wherein adjusting the gain tuning parameter comprisesadjusting the gain tuning parameter by a predetermined increment,wherein the predetermined increment corresponds to a predeterminedamount of change in the output power of the communication circuitry. 33.The method of claim 29, further comprising performing the iterations fora predetermined number of iterations.
 34. The method of claim 29,further comprising performing the iterations until the gain tuningparameter equals the initial tuning value.
 35. A method of operating atelevision system comprising the method of claim
 29. 36. A method ofoperating a cellular phone comprising the method of claim
 29. 37. Amethod of operating a media player comprising the method of claim 29.38. A calibration circuit for calibrating output power of communicationcircuitry that includes a default gain parameter, a gain tuningparameter, and a feedback loop at the communication circuitry thatadjusts the gain tuning parameter, wherein the gain tuning parameteradjusts the output power of the communication circuitry, the calibrationcircuit comprising: a tuning access circuit in communication with thegain tuning parameter, wherein the tuning parameter access circuitoperates to read the gain tuning parameter and to reset the gain tuningparameter to an initial value; and a tuning adjustment circuit incommunication with the feedback loop at the communication circuitry, andthe tuning access circuit, wherein the tuning adjustment circuitperforms a plurality of iterations at the communication circuitry thatadjusts the gain tuning parameter, the tuning adjustment circuitcomprising: circuitry that enables the feedback loop at thecommunication circuitry; circuitry that instructs the tuning parameteraccess circuit to reset the gain tuning parameter of the communicationcircuitry; circuitry that configures the gain tuning parameter of thecommunication circuitry based on the output power measurement and aprevious iteration of said gain tuning parameter; circuitry thatinstructs the tuning parameter access circuit to read the gain tuningparameter of the communication circuitry.
 39. The calibration circuit ofclaim 38, further comprising: a connection that receives a measurementof the output power of the communication circuitry; a default tuningadjustment circuit that includes a desired output power measurement andthat is in communication with the feedback loop, the connection, and thedefault gain parameter, wherein the default tuning adjustment circuitcomprises: circuitry that disables the feedback loop; circuitry thatsets the default gain parameter to a first value; circuitry thatcompares the measurement to the desired output power measurement; andcircuitry that sets the default gain parameter to a second value basedon the comparison.
 40. The calibration circuit of claim 38, furthercomprising a power detector to provide a measurement of the output powerto the tuning adjustment circuit.
 41. The calibration circuit of claim40, wherein be the output power measurement is selected from the groupconsisting of a DC signal, a pseudo-DC signal, and a low frequencysignal.
 42. The calibration circuit of claim 39, further comprising amemory that includes a table of values corresponding to a linearrelationship between the default gain parameter and the output power,wherein the default tuning adjustment circuit is in communication withthe memory and further comprises: circuitry that applies the linearrelationship to a difference between the output power measurement andthe desired output power measurement to provide a gain parameterdifference; and circuitry that applies the gain parameter difference tothe first value to provide the second value.
 43. The calibration circuitof claim 38, wherein the tuning adjustment circuit is configured toiteratively adjust the gain tuning parameter for a predetermined numberof iterations
 44. The calibration circuit of claim 38, wherein thetuning adjustment circuit is configured to iteratively adjust the gaintuning parameter until the gain tuning parameter equals zero.
 45. Atelevision system comprising the circuit of claim
 38. 46. A cellularphone comprising the circuit of claim
 38. 47. A media player comprisingthe circuit of claim 38.